[v1,2/2] drm/msm/dsi: Add 10nm dsi phy tuning configuration support

In most cases the default values of DSI PHY tuning registers
should be sufficient as they are fully optimized. However, in
some cases (for example, where extreme board parasitics cause
the eye shape to degrade), the override bits can be used to
improve the signal quality.

As per the MSM DSI PHY (10nm) tuning guideline, the drive strength
can be adjusted using DSIPHY_RESCODE_OFFSET_TOP & DSIPHY_RESCODE_OFFSET_BOT
registers, and the drive level can be adjusted using DSIPHY_CMN_VREG_CTRL
register.

Add DSI PHY tuning support for 10nm PHY. This can be extended to other
DSI PHY versions if needed.

Signed-off-by: Rajeev Nandan <quic_rajeevny@quicinc.com>
---
 drivers/gpu/drm/msm/dsi/phy/dsi_phy.c      | 55 ++++++++++++++++++++++++++++++
 drivers/gpu/drm/msm/dsi/phy/dsi_phy.h      | 23 +++++++++++++
 drivers/gpu/drm/msm/dsi/phy/dsi_phy_10nm.c | 31 +++++++++++++----
 3 files changed, 103 insertions(+), 6 deletions(-)

On Thu, 30 Dec 2021 at 12:25, Rajeev Nandan <quic_rajeevny@quicinc.com> wrote:
>
> In most cases the default values of DSI PHY tuning registers
> should be sufficient as they are fully optimized. However, in
> some cases (for example, where extreme board parasitics cause
> the eye shape to degrade), the override bits can be used to
> improve the signal quality.
>
> As per the MSM DSI PHY (10nm) tuning guideline, the drive strength
> can be adjusted using DSIPHY_RESCODE_OFFSET_TOP & DSIPHY_RESCODE_OFFSET_BOT
> registers, and the drive level can be adjusted using DSIPHY_CMN_VREG_CTRL
> register.
>
> Add DSI PHY tuning support for 10nm PHY. This can be extended to other
> DSI PHY versions if needed.

Could you please split this patch into generic code and 10nm-specific part?

>
> Signed-off-by: Rajeev Nandan <quic_rajeevny@quicinc.com>
> ---
>  drivers/gpu/drm/msm/dsi/phy/dsi_phy.c      | 55 ++++++++++++++++++++++++++++++
>  drivers/gpu/drm/msm/dsi/phy/dsi_phy.h      | 23 +++++++++++++
>  drivers/gpu/drm/msm/dsi/phy/dsi_phy_10nm.c | 31 +++++++++++++----
>  3 files changed, 103 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/gpu/drm/msm/dsi/phy/dsi_phy.c b/drivers/gpu/drm/msm/dsi/phy/dsi_phy.c
> index 8c65ef6..bf630b7 100644
> --- a/drivers/gpu/drm/msm/dsi/phy/dsi_phy.c
> +++ b/drivers/gpu/drm/msm/dsi/phy/dsi_phy.c
> @@ -669,10 +669,42 @@ static int dsi_phy_get_id(struct msm_dsi_phy *phy)
>         return -EINVAL;
>  }
>
> +static int dsi_phy_parse_dt_per_lane_cfgs(struct platform_device *pdev,
> +                                         struct dsi_phy_per_lane_cfgs *cfg,
> +                                         char *property)
> +{
> +       int i = 0, j = 0;
> +       const u8 *data;
> +       u32 len = 0;
> +
> +       data = of_get_property(pdev->dev.of_node, property, &len);
> +       if (!data) {
> +               DRM_DEV_ERROR(&pdev->dev, "couldn't find %s property\n", property);
> +               return -EINVAL;
> +       }
> +
> +       if (len != DSI_LANE_MAX * cfg->count_per_lane) {
> +               DRM_DEV_ERROR(&pdev->dev, "incorrect phy %s settings, exp=%d, act=%d\n",
> +                      property, (DSI_LANE_MAX * cfg->count_per_lane), len);
> +               return -EINVAL;
> +       }
> +
> +       for (i = 0; i < DSI_LANE_MAX; i++) {
> +               for (j = 0; j < cfg->count_per_lane; j++) {
> +                       cfg->val[i][j] = *data;
> +                       data++;
> +               }
> +       }
> +
> +       return 0;
> +}
> +
>  static int dsi_phy_driver_probe(struct platform_device *pdev)
>  {
>         struct msm_dsi_phy *phy;
>         struct device *dev = &pdev->dev;
> +       struct dsi_phy_per_lane_cfgs *strength;
> +       struct dsi_phy_per_lane_cfgs *level;
>         u32 phy_type;
>         int ret;
>
> @@ -707,6 +739,29 @@ static int dsi_phy_driver_probe(struct platform_device *pdev)
>         if (!of_property_read_u32(dev->of_node, "phy-type", &phy_type))
>                 phy->cphy_mode = (phy_type == PHY_TYPE_CPHY);
>
> +       /* dsi phy tuning configurations */
> +       if (phy->cfg->drive_strength_cfg_count) {
> +               strength = &phy->tuning_cfg.drive_strength;
> +               strength->count_per_lane = phy->cfg->drive_strength_cfg_count;
> +               ret = dsi_phy_parse_dt_per_lane_cfgs(pdev, strength,
> +                                               "phy-drive-strength-cfg");
> +               if (ret) {
> +                       DRM_DEV_ERROR(dev, "failed to parse PHY drive strength cfg, %d\n", ret);
> +                       goto fail;
> +               }
> +       }
> +
> +       if (phy->cfg->drive_level_cfg_count) {
> +               level = &phy->tuning_cfg.drive_level;
> +               level->count_per_lane = phy->cfg->drive_level_cfg_count;
> +               ret = dsi_phy_parse_dt_per_lane_cfgs(pdev, level,
> +                                               "phy-drive-level-cfg");
> +               if (ret) {
> +                       DRM_DEV_ERROR(dev, "failed to parse PHY drive level cfg, %d\n", ret);
> +                       goto fail;
> +               }
> +       }

After reading the code (and the way you use those values later), I'd
suggest adding the parse_dt hook instead of parsing it from the
generic code and putting the values into phy-specific data instead.
This way in the parse_dt you can read, validate and prepare register
values that are going to be written into the hardware. Then in the
phy_enable you can write those values directly, without any ifs.

> +
>         phy->base = msm_ioremap_size(pdev, "dsi_phy", "DSI_PHY", &phy->base_size);
>         if (IS_ERR(phy->base)) {
>                 DRM_DEV_ERROR(dev, "%s: failed to map phy base\n", __func__);
> diff --git a/drivers/gpu/drm/msm/dsi/phy/dsi_phy.h b/drivers/gpu/drm/msm/dsi/phy/dsi_phy.h
> index b91303a..9ff733a 100644
> --- a/drivers/gpu/drm/msm/dsi/phy/dsi_phy.h
> +++ b/drivers/gpu/drm/msm/dsi/phy/dsi_phy.h
> @@ -39,6 +39,10 @@ struct msm_dsi_phy_cfg {
>         const int quirks;
>         bool has_phy_regulator;
>         bool has_phy_lane;
> +
> +       /* phy tuning config counts per lane */
> +       u32 drive_strength_cfg_count;
> +       u32 drive_level_cfg_count;
>  };
>
>  extern const struct msm_dsi_phy_cfg dsi_phy_28nm_hpm_cfgs;
> @@ -81,6 +85,24 @@ struct msm_dsi_dphy_timing {
>  #define DSI_PIXEL_PLL_CLK              1
>  #define NUM_PROVIDED_CLKS              2
>
> +#define DSI_LANE_MAX                   5
> +#define DSI_MAX_SETTINGS               8
> +
> +/**
> + * struct dsi_phy_per_lane_cfgs - Holds register values for PHY parameters
> + * @val: Register values for all lanes
> + * @count_per_lane: Number of values per lane.
> + */
> +struct dsi_phy_per_lane_cfgs {
> +       u8 val[DSI_LANE_MAX][DSI_MAX_SETTINGS];
> +       u32 count_per_lane;
> +};
> +
> +struct msm_dsi_phy_tuning_cfg {
> +       struct dsi_phy_per_lane_cfgs drive_strength;
> +       struct dsi_phy_per_lane_cfgs drive_level;
> +};
> +
>  struct msm_dsi_phy {
>         struct platform_device *pdev;
>         void __iomem *base;
> @@ -98,6 +120,7 @@ struct msm_dsi_phy {
>
>         struct msm_dsi_dphy_timing timing;
>         const struct msm_dsi_phy_cfg *cfg;
> +       struct msm_dsi_phy_tuning_cfg tuning_cfg;
>
>         enum msm_dsi_phy_usecase usecase;
>         bool regulator_ldo_mode;
> diff --git a/drivers/gpu/drm/msm/dsi/phy/dsi_phy_10nm.c b/drivers/gpu/drm/msm/dsi/phy/dsi_phy_10nm.c
> index d8128f5..ac974c06 100644
> --- a/drivers/gpu/drm/msm/dsi/phy/dsi_phy_10nm.c
> +++ b/drivers/gpu/drm/msm/dsi/phy/dsi_phy_10nm.c
> @@ -775,10 +775,20 @@ static void dsi_phy_hw_v3_0_lane_settings(struct msm_dsi_phy *phy)
>                 dsi_phy_write(lane_base + REG_DSI_10nm_PHY_LN_CFG2(i), 0x0);
>                 dsi_phy_write(lane_base + REG_DSI_10nm_PHY_LN_CFG3(i),
>                               i == 4 ? 0x80 : 0x0);
> -               dsi_phy_write(lane_base +
> -                             REG_DSI_10nm_PHY_LN_OFFSET_TOP_CTRL(i), 0x0);
> -               dsi_phy_write(lane_base +
> -                             REG_DSI_10nm_PHY_LN_OFFSET_BOT_CTRL(i), 0x0);
> +
> +               /* platform specific dsi phy drive strength adjustment */
> +               if (phy->cfg->drive_strength_cfg_count) {

Something is not correct here. You are checking the
phy->cfg->drive_strength_cfg_count (which should be always set for 10
nm), but then you are writing the values without checking if they were
provided or not.

> +                       dsi_phy_write(lane_base + REG_DSI_10nm_PHY_LN_OFFSET_TOP_CTRL(i),
> +                               phy->tuning_cfg.drive_strength.val[i][0]);
> +                       dsi_phy_write(lane_base + REG_DSI_10nm_PHY_LN_OFFSET_BOT_CTRL(i),
> +                               phy->tuning_cfg.drive_strength.val[i][1]);
> +               } else {
> +                       dsi_phy_write(lane_base +
> +                                     REG_DSI_10nm_PHY_LN_OFFSET_TOP_CTRL(i), 0x0);
> +                       dsi_phy_write(lane_base +
> +                                     REG_DSI_10nm_PHY_LN_OFFSET_BOT_CTRL(i), 0x0);
> +               }
> +
>                 dsi_phy_write(lane_base + REG_DSI_10nm_PHY_LN_TX_DCTRL(i),
>                               tx_dctrl[i]);
>         }
> @@ -834,8 +844,13 @@ static int dsi_10nm_phy_enable(struct msm_dsi_phy *phy,
>         /* Select MS1 byte-clk */
>         dsi_phy_write(base + REG_DSI_10nm_PHY_CMN_GLBL_CTRL, 0x10);
>
> -       /* Enable LDO */
> -       dsi_phy_write(base + REG_DSI_10nm_PHY_CMN_VREG_CTRL, 0x59);
> +       /* Enable LDO with platform specific drive level/amplitude adjustment */
> +       if (phy->cfg->drive_level_cfg_count) {
> +               dsi_phy_write(base + REG_DSI_10nm_PHY_CMN_VREG_CTRL,
> +                       phy->tuning_cfg.drive_level.val[0][0]);
> +       } else {
> +               dsi_phy_write(base + REG_DSI_10nm_PHY_CMN_VREG_CTRL, 0x59);
> +       }

And this is even worse. If the drive_level_cfg_count is set, but the
values were not provided in the DTS, you end up writing zero to the
register, thus breaking backwards compatibility.

>
>         /* Configure PHY lane swap (TODO: we need to calculate this) */
>         dsi_phy_write(base + REG_DSI_10nm_PHY_CMN_LANE_CFG0, 0x21);
> @@ -941,6 +956,8 @@ const struct msm_dsi_phy_cfg dsi_phy_10nm_cfgs = {
>         .max_pll_rate = 3500000000UL,
>         .io_start = { 0xae94400, 0xae96400 },
>         .num_dsi_phy = 2,
> +       .drive_strength_cfg_count = 2,
> +       .drive_level_cfg_count = 1,
>  };
>
>  const struct msm_dsi_phy_cfg dsi_phy_10nm_8998_cfgs = {
> @@ -963,4 +980,6 @@ const struct msm_dsi_phy_cfg dsi_phy_10nm_8998_cfgs = {
>         .io_start = { 0xc994400, 0xc996400 },
>         .num_dsi_phy = 2,
>         .quirks = DSI_PHY_10NM_QUIRK_OLD_TIMINGS,
> +       .drive_strength_cfg_count = 2,
> +       .drive_level_cfg_count = 1,
>  };
> --
> 2.7.4
>


--
With best wishes

Dmitry